6.1 Imageto usage

Usually there are two prerequisites to extracting a usable font from an
image file. First, looking at the image, so you can see what you've
got. Second, preparing the IFI file describing the contents of the
image: the character codes to output, any baseline adjustment (as for,
e.g., `j'), and how many pieces each character has. Each
is a separate invocation of Imageto; the first time with either the
`-strips' or `-epsf' option, the second time with neither.

In the second step, Imageto considers the input image as a series of
image rows. Each image row consists of all the scanlines between
a nonblank scanline and the next entirely blank scanline. (A
scanline is a single horizontal row of pixels in the image.)
Within each image row, Imageto looks top-to-bottom, left-to-right, for
bounding boxes: closed contours, i.e., an area whose edge
you can trace with a pencil without lifting it.

For example, in the following image Imageto would find two image rows,
the first from scanlines 1 to scanline 7, the second consisting of only
scanline 10. There are six bounding boxes in the first image row, only
one in the second. (This example also shows some typical problems in
scanned images: the baseline of the `m' is not aligned with those
of the `i', `j', and `l'; a meaningless black line is
present; the `i' and `j' overlap.)